1. Field of the Invention
The present invention relates to a combustor for a gas turbine engine, utilizing a combination of a diffusion combustion system and a premixing/pre-evaporating combustion system, or a combustor for a gas turbine engine, including a premixing/pre-evaporating chamber.
2. Description of the Related Art
Combustors for a gas turbine engine are already known from U.S. Pat. No. 4,589,260 and Japanese Patent Application Laid-open No. 7-332671. A first fuel nozzle for diffusion combustion disposed on the axis of the gas turbine engine combustor of the latter publication, is designed to inject fuel under pressure directly into a combustion chamber. A second fuel nozzle for premixing/pre-evaporating combustion disposed to surround an outer periphery of the first fuel nozzle, includes a louver disposed within an annular premixing/pre-evaporating chamber in which a swirled air flow generated by a swirler flows; and is designed to atomize the fuel injected from a fuel injecting port into the premixing/pre-evaporating chamber by collision of the fuel against the louver.
The combustor for the gas turbine engine of the above-described Japanese publication suffers from a problem that it is difficult to sufficiently atomize fuel, resulting in a degraded emission characteristic, because the first fuel nozzle injects the fuel under pressure directly into the combustion chamber. The combustor also suffers from another problem that it is difficult to appropriately design the shape of the louver and the relative positional relationship between the louver and the fuel injection port, because the fuel injected from the fuel injection port by the second fuel nozzle must be atomized by collision against the louver, and also the number of parts is increased due to the provision of the louver.
The combustor for the gas turbine engine of the above-described Japanese publication includes an annular premixing/pre-evaporating chamber surrounding the axis, and a homogeneous combustion chamber connected to a downstream portion of the premixing/pre-evaporating chamber, so that the air and fuel fed to the premixing/pre-evaporating chamber are supplied to the homogeneous combustion chamber in a state in which the air and fuel are atomized by generating swirled flows thereof.
In the combustor for the gas turbine engine where the premixing/pre-evaporating chamber is at a location upstream of the homogeneous combustion chamber, the following problem is encountered: A fuel-air mixture in the premixing/pre-evaporating chamber may be self-ignited by a back fire from the homogeneous combustion chamber in some cases. Particularly, in the center portion of the premixing/pre-evaporating chamber, the swirled flows stagnate, resulting in a reduced flow speed and for this reason, the self-ignition phenomenon is liable to be produced.